Electromagnetic waves attenuate as the waves penetrate into a conducting medium. As a result, the alternating current over the cross section of a conductor or the alternating magnetic flux over the cross section of a magnetic circuit is not distributed uniformly, but is located chiefly in the surface layer. The skin effect is due to the production of eddy currents when an electromagnetic wave propagates in a conducting medium. Thus, skin effect causes high frequency electrical current to flow on surface regions of a conductive material, thereby increasing the alternating current (AC) resistance of a conductive wire to increase significantly over the direct current (DC) resistance of the conductive wire.
Further, proximity effect limits regions in which AC current flows in a plurality of conductive wires proximately placed among one another by the interaction of electromagnetic fields generated by the electrical current flowing through different conductive wires. The result of the proximity effect is further increase in the AC resistance of a plurality of conductive wires over the DC resistance of the plurality of conductive wires above the increase caused by the skin depth effect. The combination of the skin effect and the proximity effect can result in significant increase in the AC resistance of a plurality of conductive wires in high frequency applications.